The use of diagnostic assays is very well known for the diagnosis, treatment and management of many diseases. In that regard, different types of diagnostic assays have been developed to simplify the detection of various analytes in clinical samples such as blood, serum, plasma, urine, saliva, tissue biopsies, stool, sputum, skin or throat swabs and tissue samples or processed tissue samples. These assays are frequently expected to provide a fast and reliable result, while being easy to use and inexpensive to manufacture.
One common type of disposable assay device is a “dry slide” such as those described in U.S. Pat. No. 3,992,158 to Przybylowicz, et al., issued Nov. 16, 1976. This document describes an integral analytical element, the dry slide, having a sample-spreading layer in fluid contact with a superposed reagent layer. The reagent layer contains a material interactive with an analyte or a precursor of a reaction product of an analyte, and within which a detectable change in optical or electronic properties of the reagent layer can be produced by virtue of such interactive material. Such a change, which can be the generation or destruction of coloration or fluorescence, can be detected quantitatively by radiometric techniques and, if desired, by automatic radiometric sensing devices such as photometric devices. Modern diagnostic analyzers provided automated handling of dry slides and automated measurement of samples using the dry slides. This permits testing a large number of samples in a relatively short period of time.
Specifically, there are generally two different types of slide elements, each relating to a form of patient sample testing that is required. A “potentiometric” slide element, such as described by U.S. Pat. No. 4,184,936 (Paul, et al.) and U.S. Pat. No. 4,214,968 (Battaglia, et al.), incorporated herein in their entirety, includes a pair of electrodes which can be interfaced with an electrometer or other suitable test apparatus capable of detecting an electrical property produced by a deposited test sample. A “colorimetric” slide element, on the other hand, is capable of being read by a reflectometer or other suitable apparatus capable of detecting an optical property, e.g., fluorescence, produced by or deposited onto the element through a read area provided on the test element which is aligned with an optical window of the testing device. Colorimetric slide elements are further categorized as to the type of testing required. Endpoint testing, for example, requires only a single optical read after a predetermined incubation interval, while rate chemistry tests require multiple optical reads during various points of an incubation cycle.
In the field of medical diagnostics, there is a continued need to improve throughput of analyzers, e.g., to permit their use in large-volume testing centers such as reference laboratories. Various prior schemes add parallel processes to the analyzers, e.g., additional incubators, additional metering systems, or additional readers. Other schemes multiplex assays by running multiple assays on a single analyzer or running multiple analyzers at the same time. However, these prior schemes increase the size and complexity of individual analyzers or laboratories using those analyzers. Moreover, increasing throughput according to prior schemes increases the use of the hardware and can accelerate the time to failure of any given component of an analyzer. There is, therefore, a need for ways of increasing assay throughput without the aforementioned disadvantages.